National Boards > General Highway Talk
What will happen when trucks get fast?
MikieTimT:
--- Quote from: Dirt Roads on December 02, 2022, 11:10:22 AM ---Tesla has now officially delivered its first Tesla Semi Electric cab to Pepsico. The headline on one of last night's articles indicated that it was "3 years late", but I do not know whether that is a referring to a production delay or the actual delay from this procurement. I'm curious as to whether the lifecycle costs are really going to be achieved (they certainly will achieve them if truckers can get regular access to any free charging stations). But this will be our first look at "what happens when get fast" (ergo, accelerates rapidly when unloaded). Who knows, maybe NASCAR can start a new series of race truck.
https://www.msn.com/en-us/autos/news/tesla-delivers-first-semi-electric-truck-to-pepsi/ar-AA14OTpM
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It would take quite a bit of subsidy for anyone to provide free charging using megawatt level chargers. I don't see that happening with current electrical prices as well as the amount of infrastructural changes required to get them setup in the first place. To have more than a handful in any one spot pretty much requires an electrical substation setup just to handle it, unless you're doing acres of solar with Tesla Megapacks, which also won't come cheaply.
Dirt Roads:
--- Quote from: vdeane on November 01, 2022, 08:44:30 PM ---Also: regenerative braking requires that there be somewhere for that energy to go. If the battery is full at a given moment, there isn't, so no regen. I believe there are a few other circumstances where it can be disabled as well.
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--- Quote from: wxfree on December 04, 2022, 01:23:36 AM ---Perhaps the current could be run through an electric heater. Build it like a radiator, with heating elements attached to cooling fins to dissipate the heat. Include a fan to increase cooling and burn more energy. On a big truck, this wouldn't replace the friction brakes, but it would reduce the need for them like the engine brake does.
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--- Quote from: MikieTimT on December 05, 2022, 10:24:39 AM ---That's how diesel/electric locomotives brake on long descents. They use a resistive heating grid to provide a large load on the electric trucks running as generators on downhills.
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Regenerative braking often requires a large series of fans to dissipate the heat. One of the [many] reasons that locomotives turn off the regenerative braking below a certain speed is that they would need higher speed fans when the train speed (ergo, frontal wind speed) gets below a certain ability to move the necessary volume of air (in addition to the fans). Presumably, the same would be necessary for trucks with regenerative braking. It is interesting that many hybrid cars already employ regenerative braking, but those tend to be the ones with "mild hybrid" technology whereby the electric motor assist is not capable of full deceleration downgrade (or full acceleration upgrade, for that matter).
kernals12:
--- Quote from: Dirt Roads on December 05, 2022, 12:51:53 PM ---
--- Quote from: vdeane on November 01, 2022, 08:44:30 PM ---Also: regenerative braking requires that there be somewhere for that energy to go. If the battery is full at a given moment, there isn't, so no regen. I believe there are a few other circumstances where it can be disabled as well.
--- End quote ---
--- Quote from: wxfree on December 04, 2022, 01:23:36 AM ---Perhaps the current could be run through an electric heater. Build it like a radiator, with heating elements attached to cooling fins to dissipate the heat. Include a fan to increase cooling and burn more energy. On a big truck, this wouldn't replace the friction brakes, but it would reduce the need for them like the engine brake does.
--- End quote ---
--- Quote from: MikieTimT on December 05, 2022, 10:24:39 AM ---That's how diesel/electric locomotives brake on long descents. They use a resistive heating grid to provide a large load on the electric trucks running as generators on downhills.
--- End quote ---
Regenerative braking often requires a large series of fans to dissipate the heat. One of the [many] reasons that locomotives turn off the regenerative braking below a certain speed is that they would need higher speed fans when the train speed (ergo, frontal wind speed) gets below a certain ability to move the necessary volume of air (in addition to the fans). Presumably, the same would be necessary for trucks with regenerative braking. It is interesting that many hybrid cars already employ regenerative braking, but those tend to be the ones with "mild hybrid" technology whereby the electric motor assist is not capable of full deceleration downgrade (or full acceleration upgrade, for that matter).
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Actually, *all* hybrid cars have regenerative braking. Regenerative braking is an inherent feature of an electric motor; running it in reverse turns it into a generator.
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